ML20059F286
| ML20059F286 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 08/23/1990 |
| From: | Nichols S Maine Yankee |
| To: | Martin T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| MN-90-81, SEN-90-241, NUDOCS 9009110170 | |
| Download: ML20059F286 (4) | |
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'i-D dM MaineYankeet REbABLE EtECIAict?Y76fiiA3ii'TINfiUE /
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4, EDISON DRIVE o AUGUSTA, MAINE 04336 * (207) 622-4B68 t
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k August 23, 1990 MN-90-81;
.SEN-90-241 p:
Region I j
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UNITED STATES NUCLEAR REGULATORY COMMISSION:
475 Allendale Road.
. King of Prussia, Pennsylvania' 19406 Attention: Mr. Thomas T. Martin, Regional Administrator qt
References:
(a)
License No..DPR-36 (Docket No. 50-309) l
.(b)' USNRC Letter.to Maine Yankee-dated July 19,.1990 JInspection Report No. 50-309/90-10
Subject:
Response to Notice of Violation -
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, Inspection Report No. 50-309/90-10, Reactor Coolant System Inventory 3
Gentlemen:
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..Thisiletter responds to.th'e Notice of. Violation contained in Reference (t,).
In the'attachmentito thissletter, we have restated the violation and provided our-
.. response.
We have/also addressed our actions' to prevent recurrence of similar a
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Jpersonnel and procedural errors, j
n ShouldLyou have any questlons-on this matter,-please contact'us.
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y Very truly yours, A
$kYIN N
S.. E. Nichols -
Licensing Section Head i
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k 5 Att'achment: '
Response to Notice of Violation
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Mr. Eric'J. Leeds.
Mr.< Charles S. Marschall Document Control! Desk 4
h 9009110170 900823 SEN90241.LTR..
PDR ADOCK 05000309 i
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ATTACHMENT 3
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'10 CFR 50, Appendix B, Criterion V specifies that activitier affecting 1
quality should be prescribed by and accomplished in accordance with instructions, procedures, or drawings which include appropriate criteria for determining that important activities have been satisfactorily accomplished.
1 Contrary to the above, on June'4, 1990, an important activity affecting-
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V quality, reactor coolant system fill and vent, was not satisfactorily-accomplished when plant operators inadvertently drained the pressurizer and; a
F reduced inventory in the reactor coolant system, thereby reducing the margin
'I to interruption of Residual Heat Removal System operation.
- MAINE YANKEE RESPONSE The root cause of the event was an instrumentation malfunction which provided misleading pressurizer level indication to the operators.
This malfunction.
- l resulted from inadequate procedure guidance to backfill pressurizer pressure-instruments. -As several pressurizer pressure instruments tap into the l
reference lines'of the affected pressurizer level transmitters, voids in the pressurizer pressure instrument lines necessarily affected the pressurizer level indication as system pressure was increased (i.e., pressure collapsed
-the voids,' water from the referonce leg filled the voids, loss of. mass from the reference-legs reduced static head on the differential pressure level transmitter).
A contributor to this event was procedural weaknesses which allowed the evolution to continue. The-procedure governing the evolution in. progress, 1-9-1, REACTOR COOLANT SYSTEM FILL AND VENT, contained no clear requirement' q
for agreement between indicators and no clear guidance for actions to be l
.taken in the event of indication anomalies.
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Immediate corrective steps which have been taken and the results
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achieved:
immediate action in response to the event was to stabilize the RCS by increasing: water inventory and venting. A root cause evaluation was initiated.- While this evaluation was in progress, and as. documented in Reference (b), the next-Serations Day Orders included a section re-emphasizing basic philosophies _ regarding believing-and acting upon instrumentation readings, stopping evolutions when unexpected conditions
. arise, importance of accurate communication, maintenance of a questioning attitude, teamwork, and taking the time to do it right.
Additionally, the shift turnover process was strengthened for the balance of the outage.
'SEN90241.LTR 1
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~ We have completed a formal evaluation of thu event.
Based on this
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J, s evaluation, we have completed the following:
r A task force was' established to determine the cause of the-
~ imultaneous failure of the two level chanrmis, and if other vital s
transmitters may be subject to similar common cause situations.
1 Improper venting (backfilling) of connected pressurizer pressure 7
instruments was-determined to be the cause, and actions were taken-
- to ensure these instrumr's were adequately backfilled prior to s
being' required. The faiure of other vital instruments due to a similar cause is not considered likely due to their different.
- design, o
. Procedure 1-9-1, REACTOR COOLANT SYSTEM FILL AND VENT, was:
extensively rewritten to incorporate the recommendations from our-i.aternal evaluation:-
Guidance for stopping any evolutions which could effect pressurizer: level if any anomalies in pressurizer level
-indication exist.
Criteria for ensuring pressurizer level instruments are in agreement.
Requirements for backfilling and verifying the operability' of.
all pressurizer level instruments just prior to commencing the c
procedure.
Criteria for minimum number of operable pressurizer level transmitters.
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Realistic pressurizer level control band for the initial RCS pressurization for venting reactor coolant pump seals.
Guidance for methods to reduce RCS-inventory under all anticipated conditions.
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' Guidance'to control rate of RCS pressurization using nitrogen
~ ithin the capability of the coolant make up system.
w The collective result of these actions was that the RCS was subsequently
- successfully filled and vented without incident.
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Corrective steps which have been or will be taken to avoid further violations:
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The following additional recommendations of the task force discussed in 1, above,, are also planned to be implemented.
Revise Instrument and Controls procedures, associated with pressurizer level and pressure transmitter calibrations.and preventive maintenance, to expand precautions and incorporate steps to backfill-all affected sensing lines upon completion of calibration. This procedure revision is scheduled for completion prior to our next -scheduled refueling outage.
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..SEN90241.LTR 2
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= Review additional applicable procedures for other vital I
differential pressure' instrumentation to' ensure requirements for L
adequate backfill following calibration,is included. This review 4
and resulting )rocedure changes are scheduled for completion prior a
to our next scleduled refueling outage, I
Procedure 1-26-4, RESPONSIBILITIES AND AUTHORITIES OF OPERATING l
PERSONNEL, is being reviewed to ensure that it is consistent and
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adequately emphasizes key aspects of current operating philosophy relative to believing and acting upon instrumentation readings and-l' stopping ovolutions when unexpected conditions arise.
This review and necessary procedure changes will. be in effect by October 31, 1990.
The Manager, Operations Department is scheduled to meet with each of the-p six operating crews during the first block of the Licensed Operator Requalification Course (LORC) to review aspects of this evert relative v
to what operating personnel could have done to prevent it ahd to.
m re-emphasize current department philosophy relative to plant operations as, stated in the department's " Operating Philosophy Guidelines for Plant.
Shift Superintendents and Shift Operating Supervisors",
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These actions are intended to prevent recurrence of similar personnel l
and procedural errors.
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Date when full compliance was achieved:
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Full compliance was achieved on June 4,1990, when the evolution' resulting in:the violation was stopped and the RCS placed in a stable condition.
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